The present invention relates to tissue products comprising a lubricating formulation for transfer to the skin upon use. More particularly, the present invention relates to facial and bath tissue comprising a lubricating formulation comprising an emollient, a structurant, and a rheology enhancer. The novel lubricating formulation has improved stability and enhanced aesthetics, and transfers easily from the tissue to skin upon use.
Many absorbent tissue products, such as facial tissue, bath tissue, paper towels, and napkins are used to absorb and remove bodily fluids, make-up, and other soils, and leave the skin clean and dry. During repeated use, however, many tissue products can also abrade the skin and remove the natural protective oils and lipids from the skin=s surface. For example, during frequent nose blowing or anal cleansing, the skin may be compromised and can become so abraded as to become red and sore to the touch. In this state, additional irritants can penetrate the outer layers of the skin and cause further irritation, and even infection.
In order to address these concerns, there have been numerous previous attempts to reduce the abrasive effect of bath and facial tissues and to increase their softness impression. One common approach to increase the softness of tissue products is by closely controlling the mechanical processing of the tissue. By using particular processing steps during papermaking, bath and facial tissue products can be made that are softer and less irritating when used on the skin. Examples of tissue products that are mechanically processed to be softer are shown in U.S. Pat. No. 4,300,981 (Carstens), issued Nov. 17, 1981, as well as the various patents discussed in its specification.
Besides mechanical processing, others have applied emollients, salves, cleansing agents, and the like to tissue products to enhance not only the cleaning of the skin, but also to reduce irritation and inflammation by depositing a protective layer on the skin surface. This reduction in irritation and inflammation is typically achieved through either the lubricity of the substance applied to the tissue or through the therapeutic action of the substance itself. This approach is illustrated in U.S. Pat. No. 4,112,167 (Dake et al.) issued Sep. 5, 1978, particularly in regard to bath tissues. See also in U.S. Pat. No. 3,896,807 (Buchalter), issued Jul. 29, 1975 and in U.S. Pat. No. 3,814,096 (Weiss et al.), issued Jun. 4, 1974 for other examples of this approach.
One specific substance that has been applied as a lotion to tissue products to impart a soothing, lubricious feel is mineral oil. Mineral oil (also known as liquid petrolatum) is a mixture of various liquid hydrocarbons obtained by distilling the high-boiling (i.e., 300° C.-390° C.) fractions in petroleum. Mineral oil is liquid at ambient temperatures (i.e., 20° C.-25° C.). As a result, mineral oil is relatively fluid and mobile, even when applied to tissue products. Because mineral oil is fluid and mobile at ambient temperatures, it tends not to remain localized on the surface of the tissue, but instead migrates throughout the tissue matrix. Accordingly, relatively high levels of mineral oil need to be applied to the tissue to provide the desired softness and lotion-like feel. These levels can be as high as about 22 wt. % to about 25 wt. % of the tissue product. This leads not only to increased costs for these lotioned tissue products, but other detrimental effects as well.
One of these detrimental effects is a decrease in tensile strength of the tissue product. As mineral oil migrates to the interior of the tissue, it tends to act as a debonding agent, thus decreasing the tensile strength of the product. This debonding effect becomes more pronounced as the level of mineral oil applied is increased. Increasing the level of mineral oil applied can also adversely affect the caliper of the tissue product.
Even without increasing its level, the tendency of mineral oil to migrate into the interior of the tissue matrix once applied has other detrimental effects. For example, the applied mineral oil can transfer to, into, and through the packaging or wrapper material for the lotioned toilet tissue product. This can create the need for barrier-type packaging or wrapper films to avoid smearing or other leakage of mineral oil from the tissue product, which can result in significantly increased costs, as well as a messy package for consumers.
To date, most of the formulations, including formulations with mineral oil, have been liquids that require the addition of a high amount to the tissue to the point of feeling wet or oily in order for the formulation to transfer to the skin. Other formulations tried to date are semi-solid at room temperature, and require heating to be applied to the surface of the tissue where it is available to transfer to the user's skin. While much of the formulation does freeze on the surface of the tissue, some of the formulation penetrates to the inner portion of the tissue where it is unavailable for transfer to the skin, and may lead to one or more of the detrimental effects described above.
When applying a liquid or semi-solid lubricating formulation to a tissue product, there is always a balancing act required between applying the maximum amount of the formulation to the surface for transfer to the skin, while maintaining stability, and hence reducing the migration of the lubricating formulation or formulation components into the inner plies of the tissue product at elevated temperatures, such as those encountered during manufacturing, storage or transportation. Lubricating formulations that are too soft tend to migrate into the tissue product matrix as they do not hold the liquid portion of the semi-solid formulation. Lubricating formulations that are too hard do not transfer readily to the skin, and may flake off prior to use. As such, there is a need in the industry for lubricating formulations suitable for use in combination with tissue products that remain on the surface of the tissue, have less or no migration into the tissue product, and easily transfer to the skin surface during use without flaking to improve skin health.